Protection of the integrity of ultra thin silicon wafers with methods similar to those in the proposed invention has not been documented. Until now ultra thin wafers were formed on handle wafers. In a typical prior art operation, a device wafer is bonded to a handle wafer with a suitable bonding layer, such as silicon dioxide. See, for an example, U.S. Pat. No. 5,728,624. The bonded wafer operation requires numerous steps that could be eliminated if there was a practical method or apparatus for handling ultra thin wafers.
In comparison to thicker silicon wafers, ultra thin silicon wafers have better thermal and electrical-resistance properties in vertical power devices. Without the benefits of this invention, ultra thin silicon wafers are ordinarily subject to bowing and warping, and are vulnerable to breakage or fracture during process handling. The invention uses the inherent strength of the silicon itself, and the methods normally used to etch it, to supply a simple and effective reinforcement that enhances the physical integrity of the ultra thin region of the wafer.